Darwin was particularly influenced by the works of men of science like astronomer Sir John Herschel, traveller Alexander von Humboldt and geologist Charles Lyell. Lyell's new book, Principles of Geology (1830-3), profoundly influenced Darwin. Lyell offered not just a new geology but a new way of understanding nature. Lyell showed how tiny, slow, gradual and cumulative change over immense periods of time could produce large changes. Natural, visible, non-miraculous causes should be sought to explain natural phenomenon. Darwin had the opportunity to witness all of these forces, such as erosion, earthquakes and volcanoes, during the Beagle voyage and he became convinced that Lyell's views were correct. Darwin made several very important discoveries about the geology of South America, volcanic islands and the origins of coral reefs by building on Lyell's ideas.

According to Lyell, the landscape of the world is the product of forces that are still operating visibly around us. Small, small changes can add up over the years, centuries and millennia to produce vast mountains, deep valleys and so on. This view was known as uniformitarianism. It contrasted to more exciting scenarios requiring plenty of enormouscatastrophess. Lyell's geological uniformitarianism seems to have overdone things a bit as, on occasions, globalcatastrophess seem to have occurred regardless of his preferences.

That pattern of gradual, relatively minor change is also very much present in Darwinian evolutionary theory. Darwin, who was a geologist as well as a naturalist, knew Lyell's work inside out and much admired it.